This invention relates to the restoration or regeneration of bone lost through trauma, disease, resective surgery, and birth defects. In a more specific aspect the invention is concerned with materials capable of promoting bone growth.
Although many materials have been used for osseous wound repair, no agent currently available provides the surgeon with a predictable level of bone regeneration. Autogenous grafts and allogeneic implants are substances commonly used by surgeons to treat bone defects, and these are the result of considerable research to find an ideal material for restoration of bone. Thus, it has been known for years that bone matrix elicits a type of morphogenetic response. Because of this regeneration inducing capacity, demineralized bone matrix (DBM) has been used for repair of congenital and injury produced bone defects. However, in pediatric skeletal deficiencies, and in adults with loss of extensive amounts of bone, the individual cannot provide sufficient donor bone. In addition immunological limitations are a consideration in the use of DBM. Accordingly, other osteogenic approaches have been pursued. Such approaches include Marshall Urist's bone morphogenetic protein (BMP), and my antigen extracted, autolysed, xenogeneic (AAX) bone, which is the subject of copending application Ser. No. 447,345, filed Dec. 7, 1989.
Because they do not elicit immunologic responses, and because of the disadvantages of obtaining donor bone, ceramic compositions such as phosphate-bonded alumina and similar ceramics have been investigated as possible bone substitutes. Ceramic implants have high compressive strength; they do not degrade; they allow actual attachment of fibrous connective tissue and muscle; and they have specific gravities, coefficients of friction, strength, and surface qualities which are very similar to bone. It has been found that when ceramics are implanted, connective tissue proliferates in the pores, and trabeculae of bone are deposited on and throughout the porous structure. In addition they do not elicit an immunologic response
Whereas biodegradable and nonbiodegradable ceramic materials have been shown to offer promise as bone substitutes, biodegradable ceramics are preferred so that no surgical procedure is required to remove the ceramic. Since ceramic tricalcium phosphate is biodegradable it has been the subject of considerable research, as can be learned by referring to U.S. Pat. Nos. 4,781,183, 4,772,468, 4,610,692, 4,599,085 and 4,202,055, as well as The Journal of Orthopedic Research, Vol 3, page 301, 1985, and Proceedinqs of the 27th Annual Conference on Engineering in Medicine and Biology, 1974, Volume 16, published by The Alliance for Engineering in Medicine and Biology.
It has been found that despite the research effort the use of tricalcium phosphate ceramic materials in the regeneration of bone is still subject to improvement. The invention herein provides a distinctive form of ceramic beta tricalcium phosphate, modified to augment bone regeneration, the improvement having been reported in the Journal of Biomedical Materials Research, Vol 23, pages 17-19 (1989).